Experimental study on distributed optical fiber sensing monitoring for ground surface deformation in extra-thick coal seam mining under ultra-thick conglomerate

Abstract

The purpose of this paper is to study the law of ground surface movement and deformation in deep and extra-thick coal seam mining under ultra-thick conglomerate. With the engineering geological conditions of Qianqiu Coal Mine as the background, the three-dimensional model with the size of 3600 mm × 2000 mm × 2000 mm (length × width × height) was constructed. The distributed optical fiber sensing monitoring network is set up in the model. The optical fiber sensing signal is collected in real time by NBX-6055 demodulator to characterize the surface movement and deformation. Then based on the Mohr-Coulomb criterion, the numerical calculation model is established by using UDEC 6.0 software to explore the internal relationship between overburden and surface movement and deformation in the process of coal mining. The test results show that the distributed optical fiber monitoring technology can effectively capture the movement and deformation of ground surface. The optical fiber strain distribution curve can accurately locate the formation area and stress state of surface subsidence basin. The surface is controlled by the key strata of ultra-thick conglomerate, and in the whole process of mining, the surface movement and deformation can be roughly divided into three stages: deformation initiation, slow deformation and sudden deformation. The conclusions indicate that the distributed optical fiber sensing monitoring technology has good applicability in the surface monitoring of model test. It provides a method for the monitoring information research of mining surface movement and deformation.